This invention relates to a submersible pump and, more particularly, to a submersible pump discharge head which is strong, non-corrosive and inexpensive to produce.
It is known in the prior art to construct submersible pumps having discharge heads made from castings of iron, brass or other metals. Such metal castings were slow and expensive to produce, and they required machining. Furthermore, they were heavy and were subject to corrosion from the fluids being pumped, including corrosion from the water in wells in which many of the submersible pumps were used. Although some metals, such as brass, were more resistant to corrosion than other metals, they were also more expensive than the other metals. In addition, since the discharge heads were often connected to supporting drop pipes or delivery pipes of a dissimilar metal, galvanic couples were created between the discharge heads and the delivery pipes, causing an electric current to flow which eroded the heads and the pipes. As a result, some additional structure, such as dielectric bushings, were required to prevent the galvanic erosion of the discharge heads and the delivery pipes.
In order to overcome the shortcomings of metal discharge heads, it has heretofore been proposed to make the discharge heads of a plastic material. Although the plastic discharge heads did overcome many of the problems associated with the metal discharge heads, the plastic discharge heads were unable to withstand the forces exerted on them when they were connected to the delivery pipe. This is largely due to the fact that a threaded connection is generally used between a plastic discharge head and the delivery pipe in which the threaded end of the delivery pipe is tapered so that, as the delivery pipe is screwed farther into the threads of the discharge head, the connection becomes tighter and tighter so as to form a fluid tight seal. Thus, such a tapered threaded connection eliminates the need for a separate seal between the delivery pipe and the discharge head. However, tremendous forces, especially in the radial direction, are exerted on the discharge head during the tightening of such a tapered threaded connection, so that in many instances, the plastic discharge heads have cracked or otherwise failed under the forces.